Expression of Phosphorylated Signal Transducer and Activator of Transcription 3 and its Prognostic Significance in Canine Anal Sac Adenocarcinoma

Reduction of phosphorylated signal transducer and activator of transcription-5 expression in feline mammary carcinoma

Signal transducers and activators of transcription (STATs) are a family of transcription factors involved in various normal physiological cellular processes. Moreover, STATs have been recently identified as novel therapeutic targets for various human tumors. STAT3, STAT5a, and STAT6 have been suggested to be involved in tumorigenesis in human breast cancer. Owing to the similarity between feline mammary carcinomas (FMCs) and human breast cancers, these factors may play an important role in FMCs. However, studies on the expression of STATs in animal tumors are limited. Therefore, in this study, we aimed to characterize the expression of total STAT5 (tSTAT5) and phosphorylated STAT5 (pSTAT5) in FMCs, feline mammary adenomas, non-neoplastic proliferative mammary gland lesions, and normal feline mammary glands using immunohistochemistry. High expression of tSTAT5 was observed in the cytoplasm of all the samples assessed in this study. Moreover, high expression of tSTAT5 was observed in the nucleus; however, its levels varied depending on the lesion. The percentage of pSTAT5-nuclear positive cells varied among normal feline mammary glands (40.1 ± 25.1%), and non-neoplastic lesions, including mammary hyperplasia (43.2 ± 28.6%) and fibroadenomatous changes (18.0 ± 13.6%). Moreover, the percentage of pSTAT5-nuclear-positive cells in feline mammary adenomas was 24.5 ± 19.2%, which was significantly reduced in feline mammary carcinomas (2.4 ± 5.6%), regardless of histopathological subtype. This study suggests that decreased STAT5 activity may be involved in the development and malignant progression of feline mammary carcinomas.

Development of Monoclonal Antibodies Targeting Canine PD-L1 and PD-1 and Their Clinical Relevance in Canine Apocrine Gland Anal Sac Adenocarcinoma

Canine apocrine gland anal sac adenocarcinoma (AGASACA) is an aggressive canine tumor originating from the anal sac glands. Surgical resection, with or without adjuvant chemotherapy, represents the standard of care for this tumor, but the outcome is generally poor, particularly for tumors diagnosed at an advanced stage. For this reason, novel treatment options are warranted, and a few recent reports have suggested the activation of the immune checkpoint axis in canine AGASACA. In our study, we developed canine-specific monoclonal antibodies targeting PD-1 and PD-L1. A total of 41 AGASACAs with complete clinical and follow-up information were then analyzed by immunohistochemistry for the expression of the two checkpoint molecules (PD-L1 and PD-1) and the presence of tumor-infiltrating lymphocytes (CD3 and CD20), which were evaluated within the tumor bulk (intratumor) and in the surrounding stroma (peritumor). Seventeen AGASACAs (42%) expressed PD-L1 in a range between 5% and 95%. The intratumor lymphocytes were predominantly CD3+ T-cells and were positively correlated with the number of PD-1+ intratumor lymphocytes (ρ = 0.36; p = 0.02). The peritumor lymphocytes were a mixture of CD3+ and CD20+ cells with variable PD-1 expression (range 0-50%). PD-L1 expression negatively affected survival only in the subgroup of dogs treated with surgery alone (n = 14; 576 vs. 235 days). The presence of a heterogeneous lymphocytic infiltrate and the expression of PD-1 and PD-L1 molecules support the relevance of the immune microenvironment in canine AGASACAs and the potential value of immune checkpoints as promising therapeutic targets.

Canine Apocrine Gland Anal Sac Adenocarcinoma: A Review

Apocrine gland anal sac adenocarcinoma (AGASAC) is a relatively uncommon tumor in the dog and comprises approximately 17% of perianal malignancies; however, it is one of the most common causes of paraneoplastic hypercalcemia. Clinical signs in affected dogs most commonly are associated with mechanical obstruction caused by the primary tumor or enlarged regional metastatic lymph nodes and the effects of paraneoplastic hypercalcemia when present. Surgical excision of the primary tumor and metastasectomy of affected locoregional lymph nodes is the preferred initial treatment option for most dogs, although radiation therapy and adjuvant chemotherapy are commonly incorporated into multi-modality treatment plans. A significant role for the use of adjuvant chemotherapy has not been clearly demonstrated. Prolonged survival times are possible, especially for dogs with smaller primary tumors and for dogs that undergo further treatments for recurrent disease. In this article, we review the clinical signs, diagnosis, staging, treatment, and prognosis of AGASAC in the dog.